TIA Portal 15.1 SIMATIC ET 200SP CPU 1512SP-1 PN

[OBADA]

hello friends ,

i finished programming my project on tia portal 15.1 for CPU and PC HMI

now i want to buy all the hardware and a Siemens Memory card to download the program to CPU and start operating

how can i know what is the suitable SD card size before i buy it

i am really confused

please advice

and thanks for helping in advance